282
R. M. C. DAWSON
suggests that the synthesis of phosphoglyceride in vivo is via the same
cytidine coenzyme pathway indicated by the characterization of enzymes
in vitro and also that one pathway for the catabolism of lecithin and
phosphatidylethanolamine involves the formation of glycerylphosphorylbase intermediaries. Thus tissues have been shown to contain all the
necessary intermediaries for both the synthesis and breakdown via
these pathways, e.g., phosphorylcholine and phosphorylethanolamine,
cytidine diphosphate choline and cytidine diphosphate ethanolamine,
phosphatidic acid, glycerylphosphorylcholine and glycerylphosphorylethanolamine. More direct evidence has, however, been obtained by
examining the phosphoglycerides and these intermediaries for precursorproduct relationships after the injection of radioactive isotopes. In this
way it has been shown that the glycerylphosphorylcholine and glycerylphosphorylethanolamine in rat liver are on the pathway of lecithin and
phosphatidylethanolamine degradation and that the phosphorylcholine
could not have possibly been formed by catabolism (109, 110). Similar
results have been found for the sheep thyroid gland (24).
In more extensive isotopic studies on rat brain, evidence was obtained
that the synthetic pathway for lecithin P in vivo is via phosphorylcholine and cytidine diphosphate choline and that the degradation is
via glycerylphosphorylcholine (111).
References
1. G. Popjak and M. L. Beeckmans, Biochem. J. 46, 99 (1950).
2. E. A. Marples and R. H. S. Thompson, Biochem. J. 74, 123 (1960).
2a. W. E. M. Lands, /. Biol. Chem. 235, 2233 (1960).
3. J. Wittenberg and A. Kornberg, /. Biol. Chem. 202, 431 (1953).
4. R. M. C. Dawson, Biochem. J. 68, 352 (1958).
5. G. B. Ansell and R. M. C. Dawson, Biochem. J. 50, 241 (1951).
6. E. P. Kennedy and S. B. Weiss, /. Biol. Chem. 222, 193 (1956).
7. L. F. Borkenhagen and E. P. Kennedy, /. Biol. Chem. 227, 951 (1957).
8. W. C. McMurray, K. P. Strickland, J. F. Berry, and R. J. Rossiter, Biochem.
J. 66, 634 (1957).
9. H. G. Williams-Ashman and J. Banks, J. Biol. Chem. 223, 509 (1956).
10. S. B. Weiss, S. W. Smith, and E. P. Kennedy, /. Biol. Chem. 231, 53 (1958).
11. R. J. Rossiter, I. M. McLeod, and K. P. Strickland, Can. }. Biochem. and
Physiol 35, 945 (1957).
12. S. W. Smith, S. B. Weiss, and E. P. Kennedy, /. Biol. Chem. 228, 915 (1957).
13. L. E. Hokin and M. R. Hokin, /. Biol Chem. 234, 1387 (1959).
14. C. Bublitz and E. P. Kennedy, /. Biol. Chem. 211, 951 (1954).
15. O. Wieland and M. Suyter, Biochem. Z. 329, 320 (1957).
16. A. Kornberg and W. E. Pricer, Jr., /. Biol. Chem. 204, 345 (1953).
17. R. M. C. Dawson, Biochim. et Biophys. Ada 14, 374 (1954).
18. M. Sribney and E. P. Kennedy, /. Biol. Chem. 233, 1315 (1958).
R. M. C. DAWSON
suggests that the synthesis of phosphoglyceride in vivo is via the same
cytidine coenzyme pathway indicated by the characterization of enzymes
in vitro and also that one pathway for the catabolism of lecithin and
phosphatidylethanolamine involves the formation of glycerylphosphorylbase intermediaries. Thus tissues have been shown to contain all the
necessary intermediaries for both the synthesis and breakdown via
these pathways, e.g., phosphorylcholine and phosphorylethanolamine,
cytidine diphosphate choline and cytidine diphosphate ethanolamine,
phosphatidic acid, glycerylphosphorylcholine and glycerylphosphorylethanolamine. More direct evidence has, however, been obtained by
examining the phosphoglycerides and these intermediaries for precursorproduct relationships after the injection of radioactive isotopes. In this
way it has been shown that the glycerylphosphorylcholine and glycerylphosphorylethanolamine in rat liver are on the pathway of lecithin and
phosphatidylethanolamine degradation and that the phosphorylcholine
could not have possibly been formed by catabolism (109, 110). Similar
results have been found for the sheep thyroid gland (24).
In more extensive isotopic studies on rat brain, evidence was obtained
that the synthetic pathway for lecithin P in vivo is via phosphorylcholine and cytidine diphosphate choline and that the degradation is
via glycerylphosphorylcholine (111).
References
1. G. Popjak and M. L. Beeckmans, Biochem. J. 46, 99 (1950).
2. E. A. Marples and R. H. S. Thompson, Biochem. J. 74, 123 (1960).
2a. W. E. M. Lands, /. Biol. Chem. 235, 2233 (1960).
3. J. Wittenberg and A. Kornberg, /. Biol. Chem. 202, 431 (1953).
4. R. M. C. Dawson, Biochem. J. 68, 352 (1958).
5. G. B. Ansell and R. M. C. Dawson, Biochem. J. 50, 241 (1951).
6. E. P. Kennedy and S. B. Weiss, /. Biol. Chem. 222, 193 (1956).
7. L. F. Borkenhagen and E. P. Kennedy, /. Biol. Chem. 227, 951 (1957).
8. W. C. McMurray, K. P. Strickland, J. F. Berry, and R. J. Rossiter, Biochem.
J. 66, 634 (1957).
9. H. G. Williams-Ashman and J. Banks, J. Biol. Chem. 223, 509 (1956).
10. S. B. Weiss, S. W. Smith, and E. P. Kennedy, /. Biol. Chem. 231, 53 (1958).
11. R. J. Rossiter, I. M. McLeod, and K. P. Strickland, Can. }. Biochem. and
Physiol 35, 945 (1957).
12. S. W. Smith, S. B. Weiss, and E. P. Kennedy, /. Biol. Chem. 228, 915 (1957).
13. L. E. Hokin and M. R. Hokin, /. Biol Chem. 234, 1387 (1959).
14. C. Bublitz and E. P. Kennedy, /. Biol. Chem. 211, 951 (1954).
15. O. Wieland and M. Suyter, Biochem. Z. 329, 320 (1957).
16. A. Kornberg and W. E. Pricer, Jr., /. Biol. Chem. 204, 345 (1953).
17. R. M. C. Dawson, Biochim. et Biophys. Ada 14, 374 (1954).
18. M. Sribney and E. P. Kennedy, /. Biol. Chem. 233, 1315 (1958).